EP1343452A1

EP1343452A1 - Inert dental glass

Info

Publication number: EP1343452A1
Application number: EP01271196A
Authority: EP
Inventors: Stefan Hoescheler; Markus Mikulla; Gabriele Rackelmann; Volker Bambach
Original assignee: 3M Espe AG
Current assignee: 3M Deutschland GmbH
Priority date: 2000-12-20
Filing date: 2001-12-13
Publication date: 2003-09-17
Anticipated expiration: 2021-12-13
Also published as: US7264665B2; WO2002049581A1; DE50105493D1; ATE289792T1; DE10063939B4; AU2002219182A1; DE10063939A1; EP1343452B1; US20040079258A1; JP2004516260A

Abstract

The invention relates to the use of ions of weakly basic oxides as linking ions for polyacids in cements, preferably polyelectrolyte cements. Suitable ions comprise elements of the scandium series, for example, Sc3+, Y3+, La3+, Ce4+ and all subsequent tri- and tetra-valent lanthanides and the ions Mg2+, Zn2+, Ga2+, In2+. The application of said ions permits a regulation of the cement reaction without surface treatment of the glass powder.

Description

Inertia dental glass

The invention relates to the use of inert glasses in dental compositions, in particular dental cements, preferably polyelectrolyte cements, which can be used without pretreatment of the glass powder surface.

Glasses are used in the dental field, particularly in the area of filling materials, as well as fastening cements and composites for crowns, bridges and inlyas. Reactive glasses, i.e. Glasses that take part in a chemical reaction are used in so-called polyelectrolyte cements, in particular glass ionomer cements.

Such polyelectrolyte cements usually comprise three components, a polyacid, in particular a carboxylic acid-containing substance, preferably in liquid form, a glass powder and water. If the three components are combined and mixed with each other, the reaction takes place with the formation of a solid that hardens over time (cement reaction).

Various raw materials are used in the manufacture of glasses, which are used in particular in glass ionomer cements. These are oxides, such as Si0 ₂ , Al2O3, CaO, fluorides, such as CaF ₂ , SrF ₂ , cryolite, hydroxides, such as Al (OH) 3, phosphates, such as ÄIP0, P ₂ O ₅ or calcium phosphates. However, silicates such as mullite or carbonates such as Na ₂ C0 ₃ , CaC0 ₃ or other mineral natural raw materials can also be used. In principle, all raw materials can also be used in a form containing water of crystallization.

In dental glasses, a considerable proportion of the oxygen is often replaced by fluorine. This is indicated by adding the element symbol F for fluorine in the description of the glass system.

Accordingly, glasses for glass ionomer cements can usually be assigned to one of the following systems, with P ₂ 0 ₅ and Na ₂ 0 in some cases being little or nonexistent: Si0 ₂ - AI2O3 - CaO - (P2O5) - (Na ₂ 0) - F

SiO≥ - AI2O ₃ - SrO - (P2O5) - (Na ₂ 0) - F

Si0 ₂ - AI2O3 - SrO - La ₂ 0 ₃ - (P ₂ 0 ₅ ) - (Na ₂ 0) - F

Si0 ₂ - AI2O3 - CaO - La ₂ 0 ₃ - (P ₂ 0 ₅ ) - (Na ₂ 0) - F

The glasses that are used in dental cements are generally fluoroaluminosilicate glasses. The acid solubility of the glass is a prerequisite for its use as a component of a polyelectrolyte cement. An acid-soluble glass structure is created when silicon is partially replaced by aluminum. However, the replacement of silicon with aluminum is only possible in the presence of basic oxides in order to balance the charge of the 3-valent aluminum ion in places of the 4-valent silicon ion.

When the polyacids and water are added, the glass structure is broken up and, in particular, the ions with network-changing properties are released at least partially as so-called cross-linking ions.

The crosslinking manifests itself in an increasing hardening of the cement over time. All at least divalent basic ions, but also the Al ³⁺ is able to form such polymeric structures. A distinction is usually made between the processing time - the point in time at which the dentist can still process the paste paste and the hardening time - the point in time after which post-processing with rotating dental instruments is possible. It has been shown that conventional glasses, which contain, for example, Ca ²⁺ and Al ³⁺ as crosslinking ^ions , are untreated too reactive and set too quickly with the polyacid because of their high solubility, so that the dental cement which forms cannot be processed properly.

It is possible to slow down the dissolution process by reducing the calcium content in the glass; however, it has been shown that if the proportion of basic oxides, such as CaO or SrO, which can dissolve is too low, the strength properties of the cement deteriorate due to insufficient ions available. This means that the dentist has only a very short time to mix and apply the filling compound. At the same time, he has to accept the disadvantage of having to wait a very long time before he can start finishing the cement. This is contrary to the requirements that a dentist places on a dental cement. The dentist usually needs a processing time of 1 to 4 minutes and a curing time of 5 to 8 minutes. The curing time is usually determined in accordance with ISO 9917 (First Edition) Part 7.3. The processing time and the curing time can be determined with a viscometer, as described in EP 0 023 013 A. In order to achieve the desired processing properties of the cement, i.e. to have enough time for processing and as little time as possible until it has completely hardened, it is customary to subject the glass powder to a surface treatment after the grinding process, as described, for example, in Clinical Materials 12, 113-115 (1993) or DE 29 29 121 A (EP 0 230 113 A). The reaction rate of the glasses which react too quickly due to their composition is adjusted to the desired level by depleting their surface of reactive ions.

EP 0 023 013 A describes the use of a calcium aluminum fluorosilicate glass powder for glass ionomer cements, to which further oxides may be added if they do not impair the properties of the glass. According to the description, the surface of the glass has to be deactivated in order to obtain a usable glass for a dental cement. Deactivation is a process in which the reaction rate of a glass powder with an acid is slowed down by a surface treatment and the desired processing times of the cement are thus set. The surface can also be deactivated by other relatively complex surface treatments, such as by coating the surface, for example with a polymer.

In EP 0 023 013 A this is done by chemical treatment of the powder surface. The result is a cement with favorable processing times and at the same time unchanged favorable mechanical material parameters.

However, this surface treatment of the glasses represents a complex process step. In addition, powder agglomerations can occur during the washing or tempering processes, which have a disadvantageous effect on the cement properties.

A glass for a bone cement is known from DE 38 06 448 A, which comprises the elements Si, Al, Ca, Sr, F, Na and P and can be made X-ray visible by adding La ₂ θ ₃ . It is emphasized that the amount of additives must not impair the properties.

The glass powder described in DE 38 04 469 A is essentially free of alkali ions and alkaline earth ions - with the exception of strontium, which is to be used in an amount of 15 to 40% by weight. DE 20 65 824 B2 describes a fluoroaluminosilicate glass powder for self-curing medical cements

An object of the present invention is to provide a glass for a dental cement, in particular a reactive glass for a polyelectrolyte cement, which is easy to manufacture. Another task can be seen in using the glass directly after the grinding process without using complex processes such as surface treatment, acid washing, coating and / or tempering. The reactivity and thus the processing and curing time then only depend on the glass composition and the grain distribution and can be produced in a simple, reproducible manner. This object is achieved by a dental composition containing a glass as described in the claims and the use of certain ions as crosslinking ions in a glass.

The invention also relates to curable compositions, in particular cements, in particular polyelectrolyte cements, which contain these glasses.

Crosslinking in the sense of the invention is understood to mean a reaction in which polyacids and at least divalent ions interact with one another in a chelation reaction, preferably an acid-base-like reaction, and lead to the formation of a polymeric network. In the present invention, the filling and fastening materials mentioned essentially mean cements, and in particular polyelectrolyte cements. Accordingly, the glass described is preferably a reactive component and not a conventional filler, in contrast to the glasses used in the composite sector, which are pure fillers and do not participate in a reaction.

Glasses for cements generally contain strongly basic ions, such as Li ⁺ , Na ⁺ , K ⁺ , Ca ²⁺ , Sr ^{2 "1"} , Ba ²⁺ , Zn ²⁺ . It has now been shown that by completely or partially replacing the strongly basic ions with weakly basic ions, such as Sc ³⁺ , Y ³⁺ , La ³⁺ such as Ce ^{3 + / 4 +} or other 2, 3, 4-valent ions the lanthanide series and / or Ga ²⁺ or ln ²⁺ , glasses are obtained which set much more slowly with polyacids.

Such glasses can surprisingly be used to produce dental cements which have a setting behavior which is desired by the dentist essentially without the usual surface treatment of the glass powder. It has also been shown that the setting times can be set in a wide range via the glass composition.

The invention has the following advantages:

By replacing the strongly basic ions such as Ca ²⁺ , Sr ²⁺ with the weakly basic ions Sc ³⁺ , Y ³⁺ , La ³⁺ Ce ^{4 + / 3 +} and other 2, 3, 4-valent ions of

Lanthanide series in glasses used in dental cements is one Controlled setting reaction of the dental cement, in particular a glass ionomer cement, can be achieved without the glass having to be surface-treated before it is used in the cement, for example by acid washing - and / or tempering. In addition to the simpler production, the advantage also lies in the better reproducibility of the processing and curing time. Although these times are not set by a surface treatment, surprisingly the desired course of setting is obtained, namely a relatively rapid transition from a state in which the cement can still be processed to a state in which the hardening begins and meaningful processing is no longer possible ,

Surprisingly, it has been found that dental compositions or cements in which the glasses mentioned are used have the same or, in some cases, even improved mechanical properties than cements in which glasses are used whose reactivity has been reduced by acid washing.

Furthermore, it was found that the cements according to the invention are hydrolytically resistant to water.

Particularly in the case of glasses which, in addition to Al and Si, contain only Y and / or La or only small amounts of more strongly reacting ions, such as Ca ²⁺ or Sr ^{2 "1"} , Ba ²⁺ , Li ⁺ , Na ⁺ , K ⁺ , these properties were found.

Furthermore, part of the oxygen can be replaced by fluorine, which improves the meltability of the glass on the one hand, and the setting behavior of the cement on the other hand, and enables the release of fluoride ions for secondary caries prophylaxis.

The previously known systems of cements are thus expanded to include the following systems.

Si0 ₂ - Al ₂ 0 ₃ - (SrO) -Ln _x O _y - P ₂ 0 ₅ - (Na ₂ 0) - F Si0 ₂ - AI2O3 - (CaO) -Ln _x O _y - P ₂ 0 ₅ - (Na ₂ 0) - F Ln _x O _y stands for an oxide of the elements Sc, Y, La to Lu. x and y can have values of 1, 2 or 3. The oxides in parentheses are only used to a small extent, if necessary not at all, since they would significantly accelerate the reaction. DE 20 65 824 A describes a glass of the system

Si0 ₂ - Al ₂ 0 ₃ - La ₂ 0 ₃ - P ₂ 0 ₅ - Na ₂ 0 - F with a Na ₂ 0 content of approx. 2% by weight.

Experiments have shown that this glass powder can only be used to bring the setting rate with polyacids into a manageable range after tempering at 400 ° C. for several hours (cf. Comparative Example 4). This is probably due to the high proportion of a strongly basic oxide, in this case a ₂ θ. Another disadvantage of a high Na ₂ 0 content is the increased water solubility of the resulting cement. It has also been found that the glasses described have essentially no phase separation or crystallization effects over a wide range of compositions.

It is to be expected that the reproducibility of the setting speed of the cement containing the glasses will improve in the case of clear glasses compared to segregated, ie cloudy, glasses, since their phase does not depend on the cooling rate.

In addition to the usual components Si0 ₂ , Al ₂ θ3, P ₂ O5, and Na ₂ 0, the glasses preferably contain essentially weakly basic and / or amphoteric ions which act as crosslinking ions during the cement reaction.

Weakly basic trivalent and tetravalent ions are preferred and particularly preferred are the ions Sc ³⁺ , Y ³⁺ , La ³⁺ , Ce ^{4 + / 3 +} and all subsequent trivalent and tetravalent ions of the lanthanide series.

According to the prevailing teaching opinion, Al ³⁺ also belongs to the weakly basic or amphoteric reacting ions. However, this takes on ^" the

Glasses a special position. Aluminum is primarily for that Acid solubility of the glass structure is responsible and only acts as a cross-linking ion. In contrast to the above-mentioned trivalent and tetravalent ions, which act as network converters, aluminum performs the task of a network builder in the glasses suitable for dental cements. The glasses used usually have a BET surface area of 1 to 15 m ² / g, preferably 2 to 8 m ² / g.

The glasses have also an average grain size (d ₅ o-value) of 0.01 to 20 .mu.m, preferably 1 .mu.m to fifth

A fraction of 0 to 25% by weight of the oxygen in the glass used is preferably replaced by fluorine, particularly preferably 8 to 18% by weight.

The pK _ß value is usually used to define the term basicity. A pK _ß of 1 can be given as the boundary between weak and strong basic. For example, the pK is _ß of Mg (OH) ₂ in RC Weast: CRC Handbook of Chemistry and Physics indicated with a value of 1, while Ca (OH) ₂ is considered to be strongly basic numbers without indication of value.

For the purposes of the present invention, weakly basic are oxides or hydroxides which dissociate only to a relatively small extent in aqueous solutions.

The following statements can be made about basicity:

From Sc to Y, the basicity to La increases. La is classified as weakly basic compared to Sr, Ba or Na and K. At the same time, the basicity decreases again from La to Lu, so that the basicity of luthetium can be compared to that of yttrium (lanthanide contraction).

Thus, all oxides and hydroxides of the Sc series can be described as weakly basic in the sense of the present invention.

The elements of the 1st main group from Li to Cs and the elements of the 2nd main group from Mg to Ba are to be classified as not weakly basic in the sense of the present invention. In addition to the base strength, the higher field strength of these ions probably also plays a certain role, as already explained. This means that the ions described are more firmly anchored in the glass structure and are therefore released more slowly. Polyacid in the sense of the present invention means a polyelectrolyte which has a polymer with ionically dissociable groups, which can be substituents on the polymer chain and the number of which is so large that the polymers are at least partially water-soluble, at least in their (partially) dissociated form. Substituents such as -COOH, -OH, -PO (OH) ₂ , -OPO (OH) ₂ , -S0 ₂ (OH) are particularly suitable for this. Organic polyacids (DE 20 61 513 A), such as polymers and copolymers of acrylic acid, methacrylic acid (EP 0 024 056 A), itaconic acid, maleic acid, citraconic acid, vinylphosphonic acid (EP 0 340 016 A; GB 22 91 060 A) are particularly preferred. In addition, if several polyelectrolytes are present, water-insoluble polyelectrolytes can also be present in the polyelectrolyte cement. The only requirement is that at least one of the polyelectrolytes is at least partially water-soluble.

The polyelectrolytes should be able to react with the glass component in the sense of a chelation reaction and / or an acid-base reaction / neutralization reaction.

The polyelectrolyte cement contains the at least partially water-soluble solid state-convertible polyelectrolyte, preferably in a proportion of 0.5 to 30% by weight, particularly preferably 2 to 25% by weight and very particularly preferably 5 to 20% by weight. In the case of polyelectrolyte cements, the addition of chelating agents to set a suitable setting is of particular importance (DE 23 19 715 A). Numerous compounds are suitable for this, in particular those which contain hydroxyl or carboxyl groups which form chelate groups or both. Particularly excellent results have been achieved with tartaric acid or citric acid, in particular with a content of 5% by weight. The addition in the form of a metal chelate also has the desired effect. The polyelectrolyte cements contain 0 to 10, preferably 0 to 5% by weight of such a compound, preferably tartaric acid.

Furthermore, the polyelectrolyte cement can have auxiliaries such as dyes, pigments, X-ray contrast agents, flow improvers, thixotropy agents, polymer thickeners or stabilizers.

Common fillers for dental materials are, for example, glass and quartz powder, plastic powder, pyrogenic highly disperse silicas and mixtures of these components.

These other additives are usually contained in the polyelectrolyte cements according to the invention in an amount of 0 to 60% by weight.

The fillers mentioned can also be rendered hydrophobic by surface treatment with organosilanes or organosiloxanes or by etherification of hydroxyl groups to alkoxy groups.

In principle, the glass compositions mentioned are also suitable for use in monomer-modified cements.

A proportion of 20 to 70% by weight, preferably 30 to 60% by weight, of weakly basic oxides in the glass has proven to be favorable.

The cement according to the invention optionally contains strongly basic oxides with a proportion in the range from 0 to 25% by weight, preferably in the range from 0 to 10% by weight.

The cement according to the invention preferably has a flexural strength in the range of at least 25 MPa to 35 MPa, particularly preferably greater than 45 MPa, measured according to ISO 4049.

The processing time of the cement, which is determined with a viscometer, is 1 to 4 minutes, particularly preferably 2 to 3 minutes. The curing time is 3 to 10 minutes, particularly preferably 4 to 8 minutes.

Preferred compositions of the glasses are given below.

In addition to the weakly basic oxides of the scandium series already mentioned, the glasses can also contain oxides of subgroups 4 and 5. Also the aluminum oxide can be partially or completely replaced by boron or gallium oxide. The melting conditions can be positively influenced by adding oxides of the 1st main group, phosphate and / or basic oxides of the 2nd main group or ZnO.

According to the invention, the oxides which are delimited from one another in the table by “+” can also be present individually. The decisive factor is the proportion by weight of the group in the glass.

Instead of the constituent "N ₂ 0 ₃ + La ₂ 0 ₃ + other lanthanide oxides", Sc ₂ 0 ₃ can also be present in an amount of 20 to 50% by weight, preferably 20 to 30% by weight are also glass compositions in which Sc ₂ 0 _{3 is} additionally contained in a comparatively small amount in addition to the above constituent.

The invention is described in more detail below with the aid of a few examples:

None of the glasses of the examples were treated with a polyacid with an inorganic acid before their reaction, which leads to a depletion of the surface of the glasses of reactive ions (acid washing).

Gas production:

Glasses with the following oxidic compositions (in% by weight) were melted at temperatures in the range from 1300 to 1600 ° C. over a period of 30 minutes to 5 hours. With the exception of Comparative Example 4, the fluorine content was 12 to 14% by weight in the sample.

In Comparative Example 4, a glass according to DE 20 65 824 A1 was melted using the following composition:

9.5 g Si0 ₂ , 10.0 g Al ₂ 0 ₃ , 7.6 g Na ₃ AIF ₆ , 9.4 g LaF ₃ , 7.3 g AIP0 ₄ . The table shows the oxidic composition.

grinding

60 to 80 g of the glass granules obtained were dry-ground in an agate vibrating mill (from Siebtechnik, grinding vessel, 100 ml, 910 rpm) with a duration of 40 to 50 min. The glass powders obtained had an average grain size in the range from 3 to 6 μm with a specific surface area from 1.8 to 2.5 m ² / g.

Example 6: Glass example 6 was additionally wet-milled with an agitator ball mill. An aluminum oxide vessel (500 ml) was filled with 50 g glass powder, 200 ml H ₂ O and 100 g zirconium oxide balls (D = 0.8 mm) and ground with a perforated zirconium oxide disc for 6 hours. The result was an average grain size of 1.5 μm and a specific surface area of 10.5 m ² .

cements

The cements were prepared by mixing the glass powder obtained with polyacids. An approx. 45% polyacrylic acid (molecular weight 20,000 to 30,000), an approx. 45% polyacrylic acid (molecular weight approx. 40,000 to 60,000) and an approx. 55% polyvinylphosphonic acid (molecular weight approx. 20,000) were used.

The setting was determined on the one hand based on ISO 9917 and on the other hand with the viscometer described in EP 0 023 013 A1. In all cases, temperature control of the samples to 28 ° C was ensured by the experimental setup. Bending strengths were determined in a three-point bending test on 2x2x25 mm cement samples according to ISO 4049. Results:

Cement 1:

Glass 1 was mixed with both a polyacrylic and a polyacrylic maleic acid in a P: F of 3: 1.

Cement 6:

Glass 6 was reacted with polyacrylic acid (45%) in a P: F of 2.0: 1.

Glass V6:

The glass was treated once and unreacted once with polyacrylic acid after 6 hours of heat treatment at 400 ° C. in a forced air oven (from Heraeus).

More cement examples:

The setting times determined for the cements obtained in Examples 1 to 9 are all in the preferred range, with the exception of glass 6, which was only ground dry.

The cement according to Comparative Example 1 presumably sets too quickly due to the high Ca content. For the cements according to the comparison Examples 2 and 3 measurement were no longer possible due to setting too fast.

For measurements with the viscometer, the first time corresponds to the processing time, the second time to the curing time. The times refer to minutes. The P: F ratio is given as a weight ratio.

The cements according to the invention are usually packaged and sold in containers. It is important to ensure that the individual components of the cement are present in such a way that there is no unwanted reaction before the intended use. The containers usually have at least two separate chambers. Suitable containers are described, for example, in WO 00/30953 A or EP 0 783 872 A.

Suitable containers are mixing capsules and closable can-shaped hollow bodies, such as screw-top glass jars. Depending on the area of application, the cements can also be packed in capsules.

Claims

claims

1. Dental composition comprising a dental glass characterized by a composition:

where instead of the component Y ₂ θ ₃ + La ₂ θ ₃ + other lanthanide oxides, SC ₂ O _{3 can also be present} in an amount of 20 to 50% by weight.

2. Dental composition according to claim 1, comprising a dental glass characterized by a composition:

where instead of the component Y ₂ O ₃ + La ₂ θ ₃ + other lanthanide oxides, Sc ₂ 0 _{3 can also be present} in an amount of 20 to 50% by weight.

3. Dental composition according to one of the preceding claims, wherein the glass is essentially a three-substance system.

4. Dental composition according to one of the preceding claims, wherein a proportion of 0 to 25 wt .-% of the oxygen in the dental glass is replaced by fluorine.

5. Dental composition according to one of the preceding claims, wherein the dental glass in powder form with a specific BET surface area of 1 to

15 m ² / g is present.

6. Dental composition according to one of the preceding claims, wherein the dental glass has an average grain size in the range of 0.01 to 10 microns.

7. Dental composition according to one of the preceding claims, wherein the surface of the dental glass has not been surface-treated to set the setting time, for example by washing with acid, surface coating and / or tempering.

8. A method for producing a dental glass as described in one of the preceding claims, comprising the steps a)

Providing the oxidic substances, b) mixing the oxidic substances, c) melting the mixture from step b), d) quenching the melt into a solid, e) grinding the solid from step d) into a glass powder, the glass powder from step d ) is not treated with acid before use in a dental cement.

9. Use of a dental glass as described in one of the preceding claims for the production of a cement, wherein the surface of the glass has not been surface-treated.

10.Use according to claim 9, wherein the cement is a polyelectrolyte cement.

11. Dental cement, comprising A) mineral solid in an amount of 50 to 90% by weight, B) water in an amount of 5 to 50% by weight and C) polyacid in an amount of 5 to 50% by weight wherein the mineral solid comprises a dental glass as described in any one of claims 1 to 8.

12. Dental cement according to claim 11, wherein in component A) the filler is present in an amount of 0 to 90% by weight.

13. Dental cement according to claim 12, wherein the filler is selected from quartz, glasses, aluminum oxide, mineral powders such as feldspar or kaolin and / or plastic powder.

14. Dental cement according to one of claims 11 to 13 with a bending strength of at least 25 MPa, measured according to ISO 4049.

15. Container with at least two chambers, containing a dental cement according to one of claims 12 to 14, wherein the flowable components are separated from the solid components.

16. A container according to claim 15 in the form of a mixing capsule.

17. Use of ions of weakly basic oxides in glasses, which can undergo a cement reaction with a polyacid, for crosslinking the polyacid.

18. Use according to claim 17, wherein the oxides are used in an amount of at least 20 wt .-%.

19. Use according to one of claims 17 or 18, wherein the oxides have a pK _ß value of> 1.

20. Use according to one of claims 17 to 19, wherein the ions of the oxides are selected from Sc ³⁺ , Y ³⁺ , La ³⁺ , Ce ⁴⁺ and all subsequent tri- and tetravalent lanthanides as well as Ga ²⁺ and / or ln ²⁺ .